Plasmapheresis is a procedure which facilitates the collection of source plasma for commerical fractionation into antihemophiliac factor (AHF), albumin, and other plasma protein fractions. During conventional plasmapheresis, a unit of whole blood is collected and separated into red cells and plasma. The red cells are returned to the donor, and the plasma is retained for fractionation purposes. Another unit of whole blood is then drawn from the donor utilizing the same phlebotomy, and the whole blood is again separated into red cells and plasma. As before, the red cells are returned to the donor, and only the plasma is retained. The end result is, for each plasmapheresis procedure, two units of source plasma for fractionation purposes.
Representative examples of disposable plasmaphersis assemblies include the following U.S. Pat. Nos:
Naftulin 3,459,182 PA1 Naftulin et al 3,782,382 PA1 Dabney 3,945,380
Representative examples of known, commercially available disposable plasmapheresis assemblies include those sold by Fenwal Laboratories (a division of Travenol Laboratories, Inc., Deerfield, Ill.); Cutter laboratories, Inc., (Berkely, Ca.); Delmed (Irvine, Ca.); and Terumo Company, Ltd., (Japan).
The nature of a typical plasmapheresis procedure demands the use of clamping devices which selectively channel and control the flow of blood and components through a given plasmapheresis assembly. Typically, several manually actuated clamping devices, such as hemostats and/or roller clamps, are used in tandem for this purpose. Use of such devices entails multiple clamping arrangements and time consuming manipulations during the procedure. The devices also introduce the possibility of operator error.
The plasmapheresis assembly discussed in the above-cited Naftulin et al document uses a manifold to interconnect the blood collection containers with the needle. The flow of fluids through the manifold is controlled by the use of inline ball valves. Such an inline valving arrangement, however, does not facilitate repetitive valving functions, because, once a ball valve is squeezed out of the fluid path to open flow communication, it cannot be easily returned to subsequently close flow communication. Furthermore, such an inline valving arrangement introduces a potentially leak-prone device into the flow paths of the assembly; could be prone to producing blood clots; and adds yet another material in contact with the blood.
It is one of the principal objects of this invention to provide a fluid control assembly which performs complex, repetitive valving operations to establish a plurality of flow modes in a given fluid circuit, such as a plasmapheresis assembly, without introducing complicated and/or leak-prone devices into the fluid circuit.
It is another one of the principal objects of this invention to provide a fluid control assembly which can be utilized to control the flow of fluids through a given fluid circuit, such as a plasmapheresis assembly, from a convenient centralized location, thereby simplifying, as much as possible, the manipulations required during the operation of the fluid circuit, and thereby minimizing, as much as possible, the chance of operator error.
It is yet another one of the principal objects of this invention to provide a fluid control assembly which can be readily incorporated into any given fluid circuit, including one utilized for plasmapheresis, without entailing major modifications to the circuit.